1. Field of the Invention
The present invention relates to a double-ended stud that serves as a component of a fastening system for holding together a pair of elements in a desired relationship. More particularly, the present invention relates to a double-ended stud with an anti-rotation arrangement for retention of the installed stud in a threaded opening.
2. Description of the Related Art
In a flanged joint of a tubular conduit, wherein the joint is defined by a pair of opposed flanges, the joint is generally held together by means of a series of axially-extending, circumferentially-disposed bolts that pass through apertures provided in each of the flanges. Such connections are readily assembled and disassembled where the flanges extend substantially perpendicularly to the adjacent outer diametral surfaces of the joined conduits, such as in conventional pipe joints or tubular casing joints. However, when flanged-end pipes or flanged-end tubular casings are to be joined together and one or more of the pipe sections or casing sections to be joined have outer pipe or casing surfaces that are inclined relative to a plane extending between the opposed flange faces, it sometimes is necessary to increase the radial extent of the flanges in order to position the bolt holes for the connecting bolts so that there is sufficient space to be able to insert and remove the bolts during assembly and disassembly of the joint.
In aircraft engine casings that define converging or diverging flow passageways, the angle of inclination of the casing surfaces and plane extending between the opposed flange faces can be of the order of about 45 degrees or more. Increasing the radial extent of such flanges to facilitate access to each side of the flanged joint can result in substantial additional engine weight, which is, of course, undesirable in an aircraft engine. To avoid the need for casing flanges having undesirably large radial lengths, it is common to maintain rather short radially-extending flanges by providing a radially-outwardly-extending flange on one component of the flanged joint and a radially-inwardly-extending flange on the other component. The radially-inwardly-extending flange is sometimes referred to as an inverted flange.
The heads of the connecting bolts of such a flange structure thus engage an inner surface of the inwardly-extending flange, one that is within the casing, rather than a surface that lies outside the casing. In such an arrangement, should one or more of the connecting bolts break, as the result of excessive torque applied during the bolt tightening operation, either upon initial assembly or upon subsequent disassembly and re-assembly for repair or overhaul of the engine, it becomes necessary to disassemble the entire casing joint, along with the low-pressure turbine case hardware, in order to be able to obtain access to and to retrieve the head portions of the broken bolts. Such disassembly and re-assembly operations consume considerable time, adding substantially to the cost of engine assembly or engine repair, should such bolt breakage occur at such flanged joints. It is desirable to provide a way of removing the retained portion of a broken connecting bolt without the need for complete disassembly of the flanged joint.
There is thus a need to provide a fastener arrangement for a flanged joint in a tubular conduit, wherein the components of the fastener arrangement are so configured as to enable the removal of one or more joint fasteners and substitution of new fasteners without the need for complete disassembly of the flanged joint.
Briefly stated, in accordance with one aspect of the present invention, there is provided a stud for interconnecting a pair of structures that each include a stud-receiving element. The stud includes a generally cylindrical shank including a first external thread adjacent to a first longitudinal end, and a second external thread adjacent to a second longitudinal end that is opposite from the first end. The first and second threads each terminate at respective inner end points that are spaced from each other and that are inwardly of the respective ends of the stud to define an unthreaded region between the first and second threads. An anti-rotation element is carried by the shank in the unthreaded region between the inner end points of the threads and extends radially outwardly from the shank. The anti-rotation element has a non-circular peripheral surface that is adapted to be engageable with a complementary locking member that is carried by one of the structures to be interconnected by the stud.
In accordance with another aspect of the present invention, a flange connection is provided for connecting together a pair of casing end flanges of a pair of end-to-end axisymmetric casings. The connection includes a first casing having at least a first end flange that extends substantially radially outwardly from the casing, and a second casing having at least a second end flange that extends substantially radially inwardly from the casing and that is engageable with the first end flange. The end flanges each include a plurality of circumferentially-spaced apertures wherein corresponding apertures are substantially co-axially aligned. The first and second casing have outer surfaces that are inclined relative to a plane defined by the contacting flanges. A stud extends through a pair of aligned apertures, wherein one end of the stud is threadedly received in one of the aligned apertures and the other end of the stud extends outwardly of the other aligned aperture and is engaged by a retaining nut to hold the pair of flanges in face-to-face relationship. An anti-rotation element is provided that is carried by the shank of the stud between the ends thereof and that extends radially outwardly from the shank. The anti-rotation element has a non-circular peripheral surface that is adapted to be engageable with a complementary locking member that is carried by one of the structures to be interconnected.